A device of this kind is known, for example, from the document EP 0 986 343 A and from the corresponding document U.S. Pat. No. 6,332,777 B, FIG. 23 to 27. A secondary part is secured on an implant by means of a screw connection and has a conically tapering head that protrudes from the implant and that has positioning projections and recesses distributed about the circumference. The secondary part is also provided with an annular groove in which an elastically deformable annular holding means of an impression cap engages in the assembled state. The impression cap also has a dimensionally stable wall at a radial distance from the holding means, and, in the assembled state, the impression cap bears with the base surface of said dimensionally stable wall on a peripheral shoulder of the implant. The holding means and the annular groove from a releasable snap-fit connection.
This known device is particularly suitable at locations of teeth of relatively large cross section. However, it is less suitable at locations of teeth of smaller cross section, for example in the front area of the lower jaw, where implants of small cross section often have to be inserted and little space is available.
U.S. Pat. No. 6,382,977 B discloses an impression element that can be fitted with a stub-like projection into the recess of an implant. The projection has spring fingers for securing releasably on the implant with a force fit. In the case of implants of small cross section, this device is unlikely to provide sufficiently reliable stability when taking an impression.